ExampleFileFilter


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35  
36  /*
37   * @(#)ExampleFileFilter.java   1.14 03/01/23
38   */
39  
40  
41  import java.io.File  ;
42  import java.util.Hashtable  ;
43  import java.util.Enumeration  ;
44  import javax.swing.*;
45  import javax.swing.filechooser.*;
46  
47  /**
48   * A convenience implementation of FileFilter that filters out
49   * all files except for those type extensions that it knows about.
50   *
51   * Extensions are of the type ".foo", which is typically found on
52   * Windows and Unix boxes, but not on Macinthosh. Case is ignored.
53   *
54   * Example - create a new filter that filerts out all files
55   * but gif and jpg image files:
56   *
57   *     JFileChooser chooser = new JFileChooser();
58   *     ExampleFileFilter filter = new ExampleFileFilter(
59   *                   new String{"gif", "jpg"}, "JPEG & GIF Images")
60   *     chooser.addChoosableFileFilter(filter);
61   *     chooser.showOpenDialog(this);
62   *
63   * @version 1.14 01/23/03
64   * @author Jeff Dinkins
65   */
66  public class ExampleFileFilter extends FileFilter {
67  
68      private static String   TYPE_UNKNOWN = "Type Unknown";
69      private static String   HIDDEN_FILE = "Hidden File";
70  
71      private Hashtable   filters = null;
72      private String   description = null;
73      private String   fullDescription = null;
74      private boolean useExtensionsInDescription = true;
75  
76      /**
77       * Creates a file filter. If no filters are added, then all
78       * files are accepted.
79       *
80       * @see #addExtension
81       */
82      public ExampleFileFilter() {
83      this.filters = new Hashtable  ();
84      }
85  
86      /**
87       * Creates a file filter that accepts files with the given extension.
88       * Example: new ExampleFileFilter("jpg");
89       *
90       * @see #addExtension
91       */
92      public ExampleFileFilter(String   extension) {
93      this(extension,null);
94      }
95  
96      /**
97       * Creates a file filter that accepts the given file type.
98       * Example: new ExampleFileFilter("jpg", "JPEG Image Images");
99       *
100      * Note that the "." before the extension is not needed. If
101      * provided, it will be ignored.
102      *
103      * @see #addExtension
104      */
105     public ExampleFileFilter(String   extension, String   description) {
106     this();
107     if(extension!=null) addExtension(extension);
108     if(description!=null) setDescription(description);
109     }
110 
111     /**
112      * Creates a file filter from the given string array.
113      * Example: new ExampleFileFilter(String {"gif", "jpg"});
114      *
115      * Note that the "." before the extension is not needed adn
116      * will be ignored.
117      *
118      * @see #addExtension
119      */
120     public ExampleFileFilter(String  [] filters) {
121     this(filters, null);
122     }
123 
124     /**
125      * Creates a file filter from the given string array and description.
126      * Example: new ExampleFileFilter(String {"gif", "jpg"}, "Gif and JPG Images");
127      *
128      * Note that the "." before the extension is not needed and will be ignored.
129      *
130      * @see #addExtension
131      */
132     public ExampleFileFilter(String  [] filters, String   description) {
133     this();
134     for (int i = 0; i < filters.length; i++) {
135         // add filters one by one
136         addExtension(filters[i]);
137     }
138     if(description!=null) setDescription(description);
139     }
140 
141     /**
142      * Return true if this file should be shown in the directory pane,
143      * false if it shouldn't.
144      *
145      * Files that begin with "." are ignored.
146      *
147      * @see #getExtension
148      * @see FileFilter#accepts
149      */
150     public boolean accept(File   f) {
151     if(f != null) {
152         if(f.isDirectory()) {
153         return true;
154         }
155         String   extension = getExtension(f);
156         if(extension != null && filters.get(getExtension(f)) != null) {
157         return true;
158         };
159     }
160     return false;
161     }
162 
163     /**
164      * Return the extension portion of the file's name .
165      *
166      * @see #getExtension
167      * @see FileFilter#accept
168      */
169      public String   getExtension(File   f) {
170     if(f != null) {
171         String   filename = f.getName();
172         int i = filename.lastIndexOf('.');
173         if(i>0 && i<filename.length()-1) {
174         return filename.substring(i+1).toLowerCase();
175         };
176     }
177     return null;
178     }
179 
180     /**
181      * Adds a filetype "dot" extension to filter against.
182      *
183      * For example: the following code will create a filter that filters
184      * out all files except those that end in ".jpg" and ".tif":
185      *
186      *   ExampleFileFilter filter = new ExampleFileFilter();
187      *   filter.addExtension("jpg");
188      *   filter.addExtension("tif");
189      *
190      * Note that the "." before the extension is not needed and will be ignored.
191      */
192     public void addExtension(String   extension) {
193     if(filters == null) {
194         filters = new Hashtable  (5);
195     }
196     filters.put(extension.toLowerCase(), this);
197     fullDescription = null;
198     }
199 
200 
201     /**
202      * Returns the human readable description of this filter. For
203      * example: "JPEG and GIF Image Files (*.jpg, *.gif)"
204      *
205      * @see setDescription
206      * @see setExtensionListInDescription
207      * @see isExtensionListInDescription
208      * @see FileFilter#getDescription
209      */
210     public String   getDescription() {
211     if(fullDescription == null) {
212         if(description == null || isExtensionListInDescription()) {
213         fullDescription = description==null ? "(" : description + " (";
214         // build the description from the extension list
215         Enumeration   extensions = filters.keys();
216         if(extensions != null) {
217             fullDescription += "." + (String  ) extensions.nextElement();
218             while (extensions.hasMoreElements()) {
219             fullDescription += ", ." + (String  ) extensions.nextElement();
220             }
221         }
222         fullDescription += ")";
223         } else {
224         fullDescription = description;
225         }
226     }
227     return fullDescription;
228     }
229 
230     /**
231      * Sets the human readable description of this filter. For
232      * example: filter.setDescription("Gif and JPG Images");
233      *
234      * @see setDescription
235      * @see setExtensionListInDescription
236      * @see isExtensionListInDescription
237      */
238     public void setDescription(String   description) {
239     this.description = description;
240     fullDescription = null;
241     }
242 
243     /**
244      * Determines whether the extension list (.jpg, .gif, etc) should
245      * show up in the human readable description.
246      *
247      * Only relevent if a description was provided in the constructor
248      * or using setDescription();
249      *
250      * @see getDescription
251      * @see setDescription
252      * @see isExtensionListInDescription
253      */
254     public void setExtensionListInDescription(boolean b) {
255     useExtensionsInDescription = b;
256     fullDescription = null;
257     }
258 
259     /**
260      * Returns whether the extension list (.jpg, .gif, etc) should
261      * show up in the human readable description.
262      *
263      * Only relevent if a description was provided in the constructor
264      * or using setDescription();
265      *
266      * @see getDescription
267      * @see setDescription
268      * @see setExtensionListInDescription
269      */
270     public boolean isExtensionListInDescription() {
271     return useExtensionsInDescription;
272     }
273 }
274
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